They were both in town for some personal business and had met at a bar. After talking and drinking they ended up fucking throughout the night, him eager to pound her tight cunt without protection and she overconfident in her birth control pills. The next morning, her cunt filled to the brim with his sperm, she left to go get ready for her day.
Later on, at a family reunion, her mom introduced her to a nice young man that was indeed the very same one she had fucked all night and still had his sperm within her and coating her panties between her legs.
Then her mom said he was her half brother she had never met…. And at almost the exact moment within her, his sperm wiggled into her egg, her birth control being defective for the past three months.